JP2012154879A - Partial discharge measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve electrical insulation and chemical corrosion resistance and further to detect partial discharge with high detection sensitivity/accuracy in a technique for detecting occurrence of partial discharge caused by pulse voltage application from a temperature change of an insulator.SOLUTION: A pulse power source 1 generates a pulse voltage of a fixed width in a fixed cycle while gradually increasing the pulse voltage in order to measure a partial discharge starting voltage and applies the pulse voltage between two enamel wires A and B of a twist pair sample. An optical fiber temperature sensor comprises two sensors 2A and 2B. The temperature sensor 2A fixes a sensor portion in contact with the twist pair sample and measures the temperature thereof, and the temperature sensor 2B separates a sensor portion from the twist pair sample for measuring a reference temperature of the twist pair sample, disposes the sensor portion in the vicinity of the twist pair sample and measures a surrounding temperature. A temperature indicator 3 determines and indicates a temperature difference ΔT (=T1-T2) between temperatures T1 and T2 measured by the temperature sensors 2A and 2B.

Description

  The present invention relates to a partial discharge measuring device that generates a partial discharge in an insulator (measurement sample) and determines insulation deterioration of the insulator based on the detection of the partial discharge, and particularly generates a partial discharge due to application of a pulse voltage. The present invention relates to a measuring device that detects a temperature change of an insulator.

  If there are minute voids in the insulator that insulates the conductors of electrical equipment such as motors, capacitors, cables, etc., the electric field concentrates on the gap due to the AC voltage or pulse voltage applied to the electrical equipment conductor A weak discharge is generated in the insulator. This discharge phenomenon is called partial discharge, and the same phenomenon occurs not only in the interior of the insulator but also in the discharge of the surface of the insulator or in the high-voltage charging portion exposed to air. The occurrence of such partial discharge advances the deterioration of the insulator, causing dielectric breakdown in the insulator due to long-term partial discharge. For example, when dielectric breakdown occurs in the winding (enameled wire) of an electric motor, Cause short circuit accidents or burning between electrodes.

  The partial discharge measuring device measures a partial discharge start voltage (PDIV) for determining the degree of insulation deterioration. The PDIV is a voltage value when the voltage applied to the insulator is gradually increased from a low value, and a partial discharge is generated in the insulator due to the voltage increase, and a voltage value when the partial discharge is first generated. It is determined that the degree of insulation deterioration progresses from the height of the lower the degree of insulation deterioration, that is, the lower the voltage value.

  The measured value of PDIV differs depending on the voltage waveform applied to the insulator, the rising speed of the applied voltage, and the partial discharge detection method. For example, there are AC voltage and pulse voltage in the applied voltage waveform, and the unipolar (single polarity) pattern that outputs multiple pulses with the same polarity as the pulse voltage, and the bipolar polarity (bipolar) that is output with the polarity reversed ) There are patterns, and these values vary depending on these measurement conditions.

  Among these measurement conditions, a method for detecting a partial discharge generated by applying a pulse voltage has become very important in measuring a partial discharge start voltage in a winding of an inverter drive motor. This is because, in the inverter drive, a failure mode different from the AC voltage is expected to occur when a voltage in the form of a pulse wave is applied to the motor winding.

  Partial discharge detection by applying a pulse voltage cannot be used in the specification of detectors used in an AC power supply, and a new detection method is considered. A method for detecting the occurrence of partial discharge due to the application of the pulse voltage and its problems are described below.

(1) Method of receiving electromagnetic waves with antenna This is a method of receiving and extracting electromagnetic waves with an antenna when partial discharge occurs. The frequency band of partial discharge is 0.7 to 5 GHz, and all or a partial band electromagnetic wave is extracted. Note that two or more antennas may be used to specify the partial discharge position.

  For example, in Patent Document 1, a signal including a partial discharge signal is detected by a current transformer (CT) or received by an antenna, and this signal is distributed to a plurality of frequency bands and converted into pulse signals, respectively, and the converted pulse signal The data distribution obtained by performing signal processing by classifying the number of pulses and extracting the data as data, dividing the signal generation time of the extracted data into ½ cycles or n cycles of the applied voltage, and processing the data. The pattern is collated with a distribution pattern of a diagnostic database in which a data distribution pattern and a noise signal distribution pattern at the time of partial discharge are stored in advance, and the presence / absence of a partial discharge signal is determined from the collation result.

  This detection method using antenna reception is a very general method, but it is greatly affected by electromagnetic noise from the surroundings (communication equipment such as mobile phones, electrical equipment, and power supplies for partial discharge detection devices), so that noise can be removed. Complicated processing is required.

(2) Method of receiving by acoustic sensor This is a method of capturing a discharge sound when a partial discharge occurs by an acoustic sensor. Similar to antenna reception, all or part of the frequency band of partial discharge is detected. Although this method is also generally used, it is affected by sound (noise) generated from the surroundings as in the case of reception of electromagnetic waves.

(3) Method of detecting discharge light Light is generated when partial discharge occurs. This is a method of capturing this light with a photomultiplier tube. This method needs to be performed in a dark room to detect light. Further, the amount of light generated by the partial discharge is very small, and an extremely high sensitivity photomultiplier tube is required.

(4) Method of measuring applied voltage distortion and impedance change When a pulsed voltage is applied to a conductor insulated by an insulator, the waveform is distorted by the influence of electromagnetic waves when the insulator is discharged. Is observed. This is a method of measuring changes in the distortion waveform and circuit impedance.

  This method is greatly affected by electromagnetic noise from the surroundings, and requires complicated processing for noise removal as in Patent Document 1.

(5) Method of measuring temperature change due to partial discharge This is a method of using a thermocouple or a resistance temperature detector as a temperature sensor and detecting partial discharge from the temperature change of the insulator due to discharge energy.

  For example, when a pulse voltage is applied between enamel wires, discharge starts to occur at a certain voltage or higher. The discharge location is a partial discharge that occurs only in a portion that is weak against an electric field. When this partial discharge occurs, heat is generated by the discharge energy and the temperature of the measurement sample is raised. It is determined whether or not partial discharge has occurred by measuring the temperature rise with a temperature sensor. Furthermore, the partial discharge start voltage (PDIV) can also be measured.

  This method eliminates the need for complicated processing for noise removal as described above, and eliminates the need for highly sensitive sensors such as photomultiplier tubes.

JP 2010-133747 A

  As described above, the method for detecting a partial discharge from the temperature change of the insulator due to the discharge energy eliminates the need for complicated processing for noise removal, as compared to other methods, and provides a photomultiplier tube or the like. A highly sensitive sensor is also unnecessary, but has the following problems.

  A thermocouple (or a resistance temperature detector) is used as a temperature sensor for measuring the temperature of the insulator. However, a normal thermocouple is covered with a stainless steel protective tube or a ceramic protective tube in order to protect the contact portion. Although the stainless steel protective tube is excellent in heat conductivity, there is a case where a short circuit accident may occur due to electric discharge because there is no electrical insulation. On the contrary, the ceramic protective tube is excellent in electrical insulation, but has poor heat conductivity, and since the thickness cannot be reduced, the thermal response is very poor. A thermocouple without a protective tube is damaged by discharge current flowing through the temperature measurement system. For this reason, the temperature measurement method using a thermocouple cannot be used for PDIV measurement performed in a state where a high voltage is applied.

  A special example is a thermocouple coated with a plastic resin (film). Compared to the stainless steel protective tube, it is slightly inferior in thermal response, but it has excellent electrical insulation. However, when it is used in a discharge electric field, it causes chemical corrosion to the resin and eventually breaks.

  An object of the present invention is a method for detecting the occurrence of partial discharge due to application of a pulse voltage from a temperature change of an insulator, which is excellent in electrical insulation and chemical corrosion resistance, and can detect partial discharge with high detection sensitivity and accuracy. It is to provide a partial discharge measuring device.

  In order to solve the above-mentioned problems, the present invention applies a pulse voltage to an insulator (measurement sample) to generate a partial discharge in the insulator, and the temperature of the insulator is an optical fiber type utilizing the thermal expansion of the optical fiber. It is measured by a temperature sensor, and the occurrence of partial discharge of the insulator is detected from this temperature change, and features the following devices.

(1) Apply a pulse voltage to the insulator to generate a partial discharge in the insulator, detect the partial discharge from the temperature change of the insulator, and determine the insulation deterioration of the insulator based on the detection A partial discharge measuring device,
An optical fiber temperature sensor for measuring the temperature of the insulator from the amount of distortion of the conduction light due to the thermal expansion of the optical fiber due to the local heat generation of the insulator due to partial discharge. Prepared,
Generation of partial discharge of the insulator is detected from a temperature change of the insulator measured by the optical fiber temperature sensor.

(2) The optical fiber type temperature sensor is
A first optical fiber temperature sensor for fixing a sensor part to the insulator and measuring a temperature of the insulator when a pulse voltage is applied to the insulator;
A sensor portion is disposed in the vicinity of the insulator, and a second optical fiber temperature sensor for measuring the ambient temperature of the insulator is provided.
Generation of partial discharge of the insulator is detected from a temperature difference between a temperature measured by the first optical fiber temperature sensor and a temperature measured by the second optical fiber temperature sensor.

(3) The optical fiber type temperature sensor is constituted by a single optical fiber type temperature sensor that measures the temperature of the insulator by fixing the sensor portion to the insulator.
From the temperature difference between the temperature of the insulator measured by the optical fiber temperature sensor when a pulse voltage is applied to the insulator and the temperature of the insulator when a pulse voltage is not applied, It is characterized by detecting the occurrence of partial discharge.

(4) A pulse power supply that is applied to the insulator while gradually increasing a pulse voltage with a constant width at a constant period,
The degree of insulation deterioration of the insulator is determined from the partial discharge start voltage PDIV when the partial discharge is generated in the insulator by the application of the pulse voltage.

  (5) The pulse power source is a unipolar pulse voltage generating means for repeatedly outputting a pulse voltage having a waveform that is likely to cause partial discharge to the insulator to either the positive electrode or the negative electrode, or a bipolar pulse that outputs the positive electrode and the negative electrode alternately. A voltage generating means is provided.

  (6) The optical fiber type temperature sensor is installed at the base position of the winding start of the motor winding to which the pulse voltage of the PWM waveform is applied, and measures the temperature of the winding.

  As described above, according to the present invention, a pulse voltage is applied to an insulator (measurement sample) to generate a partial discharge in the insulator, and the temperature of the insulator is measured using the thermal expansion of the optical fiber. Since the occurrence of partial discharge of the insulator is detected from this temperature change, the partial discharge can be detected with excellent electrical insulation and chemical corrosion resistance and high detection sensitivity and accuracy.

The block diagram of the partial discharge measuring device which shows embodiment of this invention. Explanatory drawing of the temperature measurement principle by an optical fiber type temperature sensor. Measurement results of pulse voltage waveform and partial discharge start voltage. The test result of the voltage (V) -time (t) characteristic in a unipolar pulse voltage waveform. The test result of the voltage (V) -time (t) characteristic in a bipolar pulse voltage waveform. The relationship diagram of an applied voltage and discharge charge. An example of an optical fiber temperature sensor mounting structure.

(1) Device Configuration FIG. 1 shows a configuration of a partial discharge measuring device. This figure shows a case where a twisted pair sample is used as a measurement sample, and the measurement device is composed of a pulse power source, an optical fiber temperature sensor, and a temperature display (calculator).

  In order to measure the partial discharge start voltage PDIV, the pulse power source 1 is generated while gradually increasing the voltage of a pulse (rectangular wave) having a constant width at a constant cycle, and this pulse voltage is generated by two enamel wires A, Applied between B lines. The optical fiber temperature sensor includes two sensors 2A and 2B. One temperature sensor 2A measures the temperature of the twisted pair sample itself by fixing the sensor portion to the twisted pair sample, and the other temperature sensor 2B is the twisted pair sample. In order to measure the reference temperature, the sensor portion is separated from the twisted pair sample and arranged in the vicinity thereof, and the ambient temperature of the twisted pair sample is measured. The temperature indicator 3 calculates and displays the temperature difference ΔT (= T1−T2) between the temperatures T1 and T2 measured by the temperature sensors 2A and 2B.

(2) Configuration of temperature sensor The optical fiber type temperature sensors 2A and 2B are composed of an optical fiber having a core material made of quartz glass, and the wavelength, refractive index, and transmission of light due to thermal expansion of the optical fiber. Measure temperature by capturing changes such as rate. With this configuration, the electrical insulation is very excellent, and furthermore, since the optical fiber is an inorganic material, it is less susceptible to deterioration due to partial discharge than a resin material.

  FIG. 2 is an explanatory diagram of the temperature measurement principle by the optical fiber type temperature sensor. When partial discharge is generated from the enamel wire bundle corresponding to the twisted pair samples A and B, local heat generation is caused by the discharge. In the optical fiber type temperature sensor 2A, the optical fiber which is a sensor part is thermally expanded by heat generated by the partial discharge. The amount of thermal expansion of the optical fiber is measured with high sensitivity as the amount of strain of conduction light such as a laser, and a highly accurate temperature measurement value is obtained according to the strain-temperature calibration line obtained in advance.

(3) Partial discharge detection operation In the configuration shown in FIG. 1, when a pulse power supply 1 applies a pulse voltage of a constant width to a twisted pair sample A, B while gradually increasing it at a constant period, a partial discharge is applied to the twisted pair sample with this pulse voltage. The temperature rise of the twisted pair sample varies depending on whether or not the occurrence of the occurrence of the occurrence, and the temperature at this time is measured by the temperature sensor 2A. On the other hand, the ambient temperature of the twisted pair sample (the temperature immediately before the temperature of the twisted pair sample rises) is continuously measured by the temperature sensor 2B.

  The temperature indicator 3 displays a temperature difference ΔT (= T1−T2) measured by the temperature sensor 2A and the temperature sensor 2B. When the temperature difference ΔT exceeds a certain threshold value, it is determined that partial discharge has occurred in the twisted pair samples A and B. Further, the pulse voltage generated by the pulse power supply when this determination is obtained is obtained as a partial discharge start voltage (PDIV).

  When the device configuration uses only one optical fiber temperature sensor, this temperature sensor is fixed in contact with the twisted pair sample, and the pulse voltage is applied to the twisted pair sample by gradually increasing the pulse voltage. Whether or not partial discharge has occurred in the twisted pair sample by setting the measured temperature when not applied as the reference temperature T2 of the twisted pair sample and the measured temperature when applying the pulse voltage as the measured temperature T1 of the twisted pair sample. Determination and partial discharge start voltage (PDIV) when partial discharge occurs can be obtained.

(4) Measurement of Pulse Voltage Waveform and Partial Discharge Start Voltage FIG. 3 shows the measurement results of the pulse voltage waveform and partial discharge start voltage generated by the partial discharge measuring apparatus configured in FIG.

  Here, the pulse voltage to be applied is one in which the pulse waveform is repeatedly output to one of the positive electrode and the negative electrode in the case of unipolar, and the pulse voltage waveform is output alternately in the positive and negative electrodes in the case of both polarities. FIG. 3A shows an actual pulse voltage waveform. Details of the pulse waveform are listed in Table 1. The rise time and fall time are set to less than 100 ns, and the waveform is likely to cause partial discharge due to surge.

  The optical fiber temperature sensor used was an optical fiber temperature sensor (model: FOT-L) manufactured by Fizeau Technology, Inc. and a signal conditioner, but is not particularly limited.

  The enameled wire used was KMK-20E manufactured by Hitachi Cable, with a wire diameter of φ = 0.8 mm. When a partial discharge occurs in this electric wire, the coating is destroyed in a few hours.

  FIG. 3B shows the temperature measurement result. In the case of a unipolar pulse voltage waveform, the temperature rise value (temperature difference) ΔT increases when the pulse voltage waveform exceeds 1.54 kVp-p, and therefore the PDIV in the unipolar is about 1.6 kVp-p. In the case of both polarities, since the temperature rise value (temperature difference) ΔT rises above 1.87 kVp-p, the PDIV in both polarities is about 1.9 kVp-p.

  4 and 5 are test results of voltage (V) -time (t) characteristics in a unipolar / bipolar pulse voltage waveform. In the case of the unipolar in FIG. 4, the lifetime is 120 hours or longer at 1.54 kVp-p, and partial discharge has not occurred or is below the detection limit. In the case of the bipolar shown in FIG. 5, the lifetime is 120 hours or more at 1.87 kVp-p, and partial discharge does not occur or is below the detection limit.

  The voltage at which the lifetime becomes very long by these two Vt characteristics and the maximum voltage at which the wire temperature does not increase in the temperature measurement result of FIG. That is, if the temperature rise value (temperature difference) ΔT> 0 in the partial discharge measuring apparatus according to the present embodiment, it can be determined that partial discharge has occurred.

  From the above test results, it was verified that the partial discharge start voltage of the insulator can be measured by temperature measurement using an optical fiber temperature sensor. However, it is calibrated whether or not it is responding to the discharge charge. There is a need. Therefore, using the same electric wire, the relationship between the applied voltage and the discharge charge was examined using a 50 Hz AC power supply. The result is shown in FIG.

  The discharge voltage is 110 pC (pico coulomb) at the maximum voltage (1.87 kVp-p) with no temperature rise, and it can be determined that partial discharge is occurring at a voltage higher than this. Therefore, it can be seen that the implemented device configuration can effectively measure discharge charges of 110 pC or more.

  Note that the results of FIGS. 3 and 6 are not limited to this because the measurement accuracy is improved by optimizing the temperature sensor mounting method and the discharge charge measurement method.

(5) Partial Discharge Measurement of Motor Winding The above explanation is for the case where the measurement sample is a twisted pair sample, but the partial discharge of the winding mounted on the actual motor (motor) can also be measured by the same principle. However, the mounting of the optical fiber temperature sensor has the mounting structure shown in FIG.

  FIG. 7 shows an example of a winding in the case of star connection. Although the actual iron core is cylindrical, it has a flat plate shape for explanation. As the voltage applied to the actual motor winding, when a drive current is passed from the PWM control inverter to the winding, a pulse voltage having a PWM waveform is applied and input to the motor terminal. At this time, the electric field concentrates at the winding start position of the winding, and discharge is likely to occur.

  Therefore, the optical fiber temperature sensors 2 (U) and 2 (V) are installed at the base position of the winding start. The number of sensors is one for each phase, and a pulsed voltage waveform is applied between the U and V phases (between U and W phases) to measure the temperature difference ΔT before and after energization.

A, B Enamelled wire (measurement sample)
1 Pulse power supply 2A, 2B, 2 (U), 2 (V) Optical fiber temperature sensor 3 Temperature indicator (calculator)

Claims (6)

A partial discharge is generated by applying a pulse voltage to the insulator to generate a partial discharge in the insulator, detecting the occurrence of this partial discharge from the temperature change of the insulator, and determining insulation deterioration of the insulator based on the detection A measuring device,
An optical fiber temperature sensor for measuring the temperature of the insulator from the amount of distortion of the conduction light due to the thermal expansion of the optical fiber due to the local heat generation of the insulator due to partial discharge. Prepared,
A partial discharge measuring apparatus for detecting occurrence of partial discharge of an insulator from a temperature change of the insulator measured by the optical fiber temperature sensor. The optical fiber type temperature sensor is
A first optical fiber temperature sensor for fixing a sensor part to the insulator and measuring a temperature of the insulator when a pulse voltage is applied to the insulator;
A sensor portion is disposed in the vicinity of the insulator, and a second optical fiber temperature sensor for measuring the ambient temperature of the insulator is provided.
The occurrence of partial discharge of the insulator is detected from a temperature difference between a temperature measured by the first optical fiber temperature sensor and a temperature measured by the second optical fiber temperature sensor. Item 2. The partial discharge measuring device according to Item 1. The optical fiber type temperature sensor is composed of one optical fiber type temperature sensor for fixing the sensor part to the insulator and measuring the temperature of the insulator,
From the temperature difference between the temperature of the insulator measured by the optical fiber temperature sensor when a pulse voltage is applied to the insulator and the temperature of the insulator when a pulse voltage is not applied, The partial discharge measuring apparatus according to claim 1, wherein occurrence of the partial discharge is detected. A pulse power source that is applied to the insulator while gradually increasing a pulse voltage with a constant width at a constant period,
The degree of insulation deterioration of the insulator is determined from the partial discharge start voltage PDIV when the partial discharge occurs in the insulator by the application of the pulse voltage. The partial discharge measuring device described in 1.   The pulse power source is a unipolar pulse voltage generating means for repeatedly outputting a pulse voltage having a waveform that is likely to cause partial discharge in an insulator to one of a positive electrode and a negative electrode, or a bipolar pulse voltage generating means for alternately outputting a positive electrode and a negative electrode The partial discharge measuring device according to claim 1, wherein the partial discharge measuring device is provided.   6. The optical fiber type temperature sensor is installed at a root position at the beginning of winding of an electric motor winding to which a pulse voltage of a PWM waveform is applied, and measures the temperature of the winding. The partial discharge measuring device according to claim 1.

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